1. Field of the Invention
The present invention relates to a tube which contains an X-ray opaque agent in its wall and is suitable for use as, for example, an indwelling syringe, or catheter.
2. Prior Art
There is known a tube formed from a polymer material having good compatibility with a living organism, such as a fluororesin, and containing an X-ray opaque agent, such as barium sulfate or, bismuth oxide. It is used as, for example, an indwelling syringe which is inserted in a blood vessel fixedly for the transfusion of fluids or blood. This type of syringe has the advantage that, even if an inadvertently broken part thereof may enter the vascular system in the body, it is easy to locate the part by an X-ray photograph, as it contains the X-ray opaque agent in its wall.
It is also used as a catheter which is inserted into the body of a patient for such purposes as the sampling of blood from his heart and the measurement of his blood pressure, while it is observed by fluoroscopy. Specific examples of the known tubes containing the X-ray opaque agents include one containing an X-ray opaque agent distributed uniformly through its entire wall (Japanese Patent Publication No 49394/1972), one having a wall of the triple-layered construction defined by an inner and an outer resin layer not containing any X-ray opaque agent and a middle resin layer existing between the inner and outer layers and containing an X-ray opaque agent(Japanese Patent Application laid open under No.119263/1981), and one having a wall which contains an X-ray opaque agent only in a portion when viewed circumferentially, but along its whole length, i.e., in the form of a strip of a certain width running along the length of the tube (Japanese Utility Model Application laid open under No. 108389/1976).